Although, in many physiological systems a cascade of events have been proposed between stimulation and response little is understood concerning the stimulus-secretion "coupling" process occurring in renin release from the kidney cortex. In vitro techniques are invaluable in studying this type of biological control mechanism, since the renal tissue will be isolated from the influence of varying blood pressure, nervous tone, metabolic temperature, oxygen tension, etc. The renal cortical tissue slice technique utilized in these studies is well characterized and permits the monitoring of a constant rate of renin release with the potential of altering media constituency, temperature and pharmacological agents. Since renin release from this isolated tissue is readily stimulated by, for example, beta agonists, it is possible to study the need for metabolic energy and divalent cations for this stimulated renin release. Also, the role of cAMP and prostaglandins and their intermediates in this coupling process is to be investigated. Finally, I propose to investigate the hypothesis that this "coupling" process alters renin release through changing membrane permeability, and consequently, cell volume.